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Split tracks into trips for central place foragers

Source: R/tt_split_trips.R
tt_split_trips.Rd

This function splits tracks into trips for central place foragers by identifying the trips based on a distance from the colony/nest.

Usage

tt_split_trips(
  x,
  centre_col = NULL,
  buffer_outbound = as_units(1000, "m"),
  buffer_inbound = as_units(1000, "m"),
  complete = TRUE
)

Arguments

x

A move2 object

centre_col

character string, the name of the column in the metadata table that contains the centre of the colony/nest for each track. This column must be of class sfc_POINT and should have a valid coordinate reference system (CRS) specified. The function sf_point_col() can be used to create this column.

buffer_outbound

the distance from the centre to define outbound trips, specified as a unit object, e.g as_units(10000, "m") or as_units(10, "km").

buffer_inbound

the distance from the centre to define inbound trips, specified as a unit object, e.g as_units(10000, "m") or as_units(10, "km").

complete

boolean, if TRUE, only complete trips (i.e. the ones that started in the outbound buffer and ended within the inbound buffer) are kept. If FALSE, all trips are kept, and events at the colony (i.e. in-between trips) are collected into a dummy trip labelled "trip_na".

Value

a move2 object with the trips split.

Examples

# First, add a sf point column to metadata giving nest location
show_meta(example_tt) <- show_meta(example_tt) %>%
  dplyr::mutate(nest_location = sf_point_col(nest_lon, nest_lat, crs = 4326))
# Now split the tracks into trips
example_tt_split <- tt_split_trips(
  x = example_tt,
  centre_col = "nest_location",
  buffer_outbound = as_units(1, "km"),
  buffer_inbound = as_units(1, "km"),
  complete = FALSE
)
# Now the unit of tracking is `trip_id` column
move2::mt_track_id_column(example_tt_split)
#> [1] "trip_id"
# Three incomplete trips were identified
show_meta(example_tt_split) %>%
  dplyr::group_by(track_id, trip_id, trip_type) %>%
  dplyr::summarise(.groups = "drop")
#> # A tibble: 5 × 3
#>   track_id trip_id   trip_type 
#>   <fct>    <chr>     <chr>     
#> 1 a        a_trip_1  incomplete
#> 2 b        b_trip_1  incomplete
#> 3 b        b_trip_na at_centre 
#> 4 c        c_trip_1  incomplete
#> 5 c        c_trip_na at_centre